Bell helicopter is developing a fan driven anti-torque system

Bell has revealed a groundbreaking new electric anti-torque system in development for its commercial helicopter line, one that promises enhancements to safety and operating cost, as well as a reduction in noise compared to an aircraft with a conventional tail rotor.

The electrically distributed anti-torque (EDAT) system is composed of four small fans within a tail rotor shroud in an offset two-by-two pattern. Each of the rotors contains four blades, and they are powered by four separate motors, with the electrical energy provided through generators driven by the turbine engine.

“In a nutshell, we removed all of the conventional mechanical anti-torque components — which is gearboxes, driveshafts and tail rotor hub and blades — and replaced it with four electric motors and fans,” Eric Sinusas, program director of light aircraft at Bell, told Vertical . “They are fixed-pitch blades and they’re changing rpm constantly.”

The system has been installed on a Bell 429 demonstrator aircraft at Bell’s facility in Mirabel, Quebec, and began flight testing on May 23, 2019. Since then, the program has completed about 25 flight hours, with the aircraft gradually expanding its flight envelope.

Bell is not ready to share any performance figures, but Sinusas said the feedback from the customers that have seen the system in action has been positive.

“This is the first time anyone in the world ever done this, so the first step was just to make sure that it actually works — and yes it does work,” said Sinusas. “We’re still going to be optimizing it and refining it, but the product feedback in its current configuration has been very positive.”

The system’s anti-torque fans are controlled through pedals, as with yaw control in a traditional helicopter, but the link between the pedals and the motors is entirely electric “fly-by-wire” — all mechanical linkages and the control tubes of a conventional system have been removed. Other than the tail rotor and the control mechanisms, the demonstrator aircraft is unchanged to accommodate the system, using a conventional main rotor, engine, and airframe.

Sinusas said the driving force behind the EDAT system’s development was customer feedback.

“We were looking at what are the customers demanding for aircraft? . . . And safety is obviously always at the top of the list,” he said. “This [system] certainly meets those [requirements] and it has some interesting features that conventional rotors don’t with redundancy, and when the aircraft on the ground, the electric fans are not rotating at all.”

The redundancy is extensive, with the aircraft capable of still producing a level of anti-torque thrust even if three of the four fans become inoperable.

“What it provides — unlike any conventional helicopter out there today — is the ability to give the pilot some torque authority to get down safely,” said Sinusas.

The next driver was reduced operating cost, and while Bell is not currently sharing any figures, Sinusas said removing conventional components such as lubricated gearboxes and greased bearings, and moving to a more simplified electrical system, should help keep those costs down.

Thirdly, the design promises a reduction in noise levels. “[Noise] hasn’t really been a top priority for helicopter industry for quite a while, but it’s quickly becoming a very important parameter,” said Sinusas.

The visual impact of the system is a blend of the familiar and the strange. It’s not as radical an anti-torque rethink as the tailboom fan-driven system proposed in Bell’s FCX-1 concept helicopter two years ago, or even MD’s NOTAR, which does away with the need for any type of tail rotor, but the sight of four smaller tail rotors instead of one may take a little getting used to.

And while the shrouding around the rotors certainly looks heftier than the simple vertical fin of a traditional tail rotor, Bell says the footprint is similar to that of shrouded tail rotors produced by other manufacturers (think the Fenestron on Airbus’s H145).

Sinusas said the focus of the program to date has been proof of concept rather than optimizing its performance, and the team is not working to a timeline for commercialization — at least not one that Bell is prepared to publicly disclose.

Both retrofit to existing products and incorporation into clean-sheet designs “would be an option” for the product when it does hit the market, said Sinusas, and he confirmed the technology is scalable to larger and smaller aircraft.

“It’s obviously been a secret project — we haven’t been public with it until now,” he said. “So it be interesting to see what feedback we do get.”


Wow, that looks pretty sick

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It looks ugly lol but the 429 is ugly so guess it firs

I think it looks awsome.

I know you do you Marviation 429 Check Airman pilot… Lol

The tail looks pretty stupid ngl. The rest of the chopper looks fine, but that tail just messes up the whole thing.

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true, the tail does remind me of the iphone 11

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The helicopter world is having to much fun with this,
“Gotta have 14 CFR Part 107 Cert to be an engineer at Bell!” Lol

Here are some really great Question and Answers to the EATD

Vertical: Does the EDAT system incorporate additional battery/generator capacity above the baseline aircraft?

Eric Sinusas: Yes, we added two generators specifically to power the EDAT motors, but no additional battery capacity. The generators are driven off of what was formerly the tail rotor output shaft from the main rotor gearbox.

Vertical: What happens to the system in the event of a dual engine failure?

Sinusas: When you lose both engines, the main rotor gearbox is still rotating. So because the generators are mounted off of the main rotor gearbox and not the engines, even if you lost both engines, the fact that the main rotor would be spinning in an autorotation means it would still be driving the generators.

Vertical: How much equivalent power does EDAT draw compared to a standard tail rotor?

Sinusas: We’re not getting into specifics at this point, but I can say that the power consumption and overall performance is similar to a conventional aircraft. For this, it was such a huge step to just see what the flying characteristics were of an EDAT system with a constantly changing rpm that our primary focus was on demonstrating the technology. And now that we’ve proven that the technology works and the pilot feedback is positive, the next step is getting into the optimization of the system, and answering some of those questions about energy management, and seeing where we can continue to upgrade the design.

Vertical: How well does the tail rotor shroud handle crosswinds?

Sinusas: We’re still continuing to expand the flight envelope, but we have done a series of different flights in different winds. We’ve also done right sideward flight where the helicopter is flying sideways and towards the right, and then flying sideways towards the left. We’ve done the full forward and backwards flight maneuvers. So far the handling qualities have been good and the pilot feedback has been good, saying that it handles similar to a conventional tail rotor.

The shroud design and what we put on this aircraft was what we could get to demonstrate the fundamental technology as quickly as possible, but we still have a lot of optimization to be done on the ducting as well as the rest of the system.

Vertical: How does the pilot manage the system? For example, to keep it turned on while resting on slippery surfaces, or turn it off when ground personnel are working around the aircraft?

Sinusas: The way it’s working currently is the pilot’s pedals provide a signal that goes through an algorithm and ultimately determines the speed of the motors or the fans. So the pilot is constantly managing his heading. Even when he’s on the ground, if he were on the ground on a slippery surface, he would need to manage his heading, and put in the amount of pedal that he needs to keep the aircraft where he wants it. The pilot can individually turn on and off each motor — he’s got a switch for that. But if he is on a regular, high-friction landing surface, then he simply won’t demand any rotation with his pedals. So even without turning them off, just by where his pedals are, he can have them such that they’re not rotating or slowly rotating.

In the future, because of the fly-by-wire system, we can certainly upgrade the software and the algorithms to provide more autonomy and ultimately get to the point where the pilot could take his feet completely off the pedals and have the EDAT control itself to maintain heading.

Vertical: How much anti-torque authority does the system provide with one or more fans inoperative?

Sinusas: When you lose a number of fans, you lose some of your thrust capability but not all of it. The maximum thrust design point is in right sideward flight, or the equivalent of hovering with a significant side wind hitting the aircraft broadside. But if you’re not in that condition — if you’re in a hover with no wind, let’s say, or if you’re in forward flight — you don’t need as much thrust. So you actually could have all the authority you need without all four fans.

We would say certainly if you all of a sudden lost even one of your fans, we’re going to consider that an emergency landing procedure and the pilot’s going to know that he had a failure. Our point is that because it’s only a partial failure, not a complete failure of the tail rotor, he still has some authority to help him get down safely.

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